Page 55 - IJB-7-1

Sherborne and Claeyssens
the continuous phase can act as a cosurfactant that results poliovirus through a functionalized surface against the
in smaller pores and an increased interconnectivity 99% reduction in a non-functionalized one. The filter
between the pores . could also be regenerated using either a concentrated
[32]
There is a range of research interest in emulsion electrolyte/acidic or alkaline solution depending on the
templating to create porous polyHIPE structures [42-46] . surface functionalization. A heparin-coated polyHIPE-
The research interest also extends to their potential for a based chromatographic column has also been used
range of fluid separation applications, including filters, to selectively bind Enterovirus 71 and purify it from
membranes, and chromatography [47] . There are detailed solutions, and the polyHIPE has a porosity of 0.2–0.5
reviews on emulsion templating applications [48-51] as µm and interconnected pore sizes in the range of 0.5–2
well as the range of materials and uses of a porous foam µm for the isolation of virus particles [57] . The virus can
manufactured using both liquid- and bubble-based be eluted from the column afterward.
templating [52] . Some specific reviews also detailed the Infection by airborne transmission occurs after
porous materials and uses of HIPE-based emulsions the inhalation of the contaminated droplets. Aerosol
and foam templating [53] as well as the potential of 3D transmission of virus-laden droplets is still not fully
printing as a method to produce tissue engineering understood in terms of the effects of the exhaled particle
scaffolds [54] . size distribution and the number of infectious viruses
in each particle . The virus itself is between 50 and
[11]
5. Considerations for a polyHIPE-based 200 nm in radius. Typical speech and coughing can
RPE filter against viruses produce aerosolized liquid droplets with an average size
The perspective polyHIPE filters need to be tested to of <20 µm which could linger in the air between 20 min
determine its effectiveness as a RPE filter in relation and 1 h depending on the environmental conditions;
to different porosities, thicknesses, and surface 50 and 100 µm sized particles can stay in the air for
functionalization. The average inhalation under approximately 20 s and 3 min while smaller particles can
moderate and strenuous workload 30 L/min and 85 L/ potentially remain airborne for a longer period of time.
min, respectively . To test the filter efficiency under Nevertheless, all particles pose a potential risk of being
[14]
these flow rates, typically NaCl particles are aerosolized inhaled while they remain airborne. It is important to note
using a particle generator and the particle concentration that the chances of inhalation increase as the particle size
[11]
is tested up- and downstream of the filter. This testing reduces .
can also represent aerosolized single viruses using small, The principal function of a majority of the
0.037–3.2 µm, sized particles . polyHIPE-based air filters is to remove particulates from
[14]
The porosity, chemical functionality, and mechanical the air. Vehicle exhaust fumes represent a major source
strength of the polyHIPE can be independently tuned of air pollution, for example, the hydrocarbon fragments
[58]
based on the emulsion constituents or conditions. This produced from the partial combustion of fuel . In
adjustment has led to a variety of separation-based particular, there is a need to filter out airborne particulate
applications, including filter, metal ion separation, and matter of <2.5 µm (PM ) as these particles in this size
2.5
[59]
chromatography . PolyHIPEs have a huge separation range can damage the respiratory system . According to
[55]
potential with a tunable permeability, an ability to the ISO standardized vocabulary for ultrafine particulate
alter surface chemistry, different material choices, and matter (PM), PM0.1 refers to the particulates with
interconnected pores; their uses as a filter for small aerodynamic diameters of 100 nm or less, PM2.5 with 2.5
[60]
molecule separation have been reviewed . µm, and PM10 with 10 µm . Small pollutants of <2.5
[56]
The requirements of polyHIPE specifically for µm are small enough to penetrate deep into the lungs and
the production of a respirator filter that can prevent cause damage to the alveolar walls.
the transmission of aerosolized virus-laden particles A polyHIPE-based aerosol filter for automobile
have yet to be defined. In the aspect of virus filtration, exhaust achieved an increase in the capture efficiency
there is a difference between mechanical filtration (pore of particles (<2.5 µm) from 1.2% to 72.2% after surface
[61]
size/interconnectivity) and the use of an optimally functionalisation of an amino (–NH ) end group . The
2
functionalized surface for immobilizing the virus polyHIPE filter captured these particles both on the outer
onto the polymer. Despite lacking the information surface and within the pores (pore sizes were between
regarding the pore size, an example of virus filtration 3.0 and 7.4 µm, interconnects of 1.1 and 2.4 µm), and
elaborated in the withdrawn 2008 patent EP 1 889 its effectiveness was attributed to the surface coating
811 A1 highlights the importance of a functionalized as well as the coating thickness physically reducing the
surface (aminated, sulfonated, or betainated) to interconnect and pore size. The filtering efficiency of
improve the filtration of poliovirus type 1 from water. a sample with a thickness between 1 and 14 mm rose
The presented data showed the removal of 99.99% from 65 to 80% in filtering particulates of <2.5 µm.

International Journal of Bioprinting (2021)–Volume 7, Issue 1 51